Any ideas how THIS could happen?

[wildkat]

I don't pretend to be very mechanical, but I was hoping that maybe some of you guys could help me out here.

I have a 2006 C-15 CAT, with the twin turbo in it.

I know about & have had troubles with over the course of time with the high pressure twin, but all the kinks seem to be worked out now.

This is a new one, last night on my way home I found that whenever my truck was under power, like REALLY working my "check engine" light would come on & blink a code. So like the careful o/o I am I made note of the code & contacted the Pete dealership I deal with at home. They said it was likely a sensor had gone on the blink. So I stopped in there last night after I dropped my trailer & low & behold, it was NOT a sensor at all. The rear, the one against the firewall, actuator valve had actually BROKEN! Thankfully, it broke right near the bolt hole so, the 4" piece that broke was still attached to the engine block & not banging around in the innards!

Here are a couple of pics I took to better explain...





Can anyone explain WHY this might have happened? The mechanic I deal with all the time is really used to all my dumb questions, but he just couldn't answer the WHY, except to tell me "it happens sometimes". Thankfully, the repair was covered under warranty, so at least THAT part is covered.

Thanks guys

[allan5oh]

actuator valve for the turbo?

[Maniac]

The studs broke, common problem with the newer C-15's, Cat knows all about it, but I don't think they are doing anything about it, there are upgraded studs that Cat uses, but I don't think it solved the problem, because the nuts keep loosening up.

My buddy Nick has been thru this 3 or 4 times since he got his 07 Pete (with an 06 C-15) he has 300,000 miles on it now.

[wildkat]

actuator valve for the turbo?

LMAO , no allan, I am SOOO bad when it comes to mechanical stuff...hense the pictures!

No this is "ontop"..."above" the valves...you know...right "under" the valve covers on the engine.. I had a rocker arm snap once...the mechanic took off...in order, valve cover, actuator valve, then the rocker arm.

Does that make sense?

[wildkat]

The studs broke, common problem with the newer C-15's, Cat knows all about it, but I don't think they are doing anything about it, there are upgraded studs that Cat uses, but I don't think it solved the problem, because the nuts keep loosening up.

My buddy Nick has been thru this 3 or 4 times since he got his 07 Pete (with an 06 C-15) he has 300,000 miles on it now.

So it's MORE bolt issues? What did they do? Buy a shipment of defective bolts for crissake?

LOL I've had more damned BOLT troubles than I can shake a stick at! Did he have torque bolt issues too...Mine keep breaking!

Yeah mine is an '07 too, with the last of the '06 engines. I've got 730,000 kms on mine...ummm 453,000 miles

[allan5oh]

OK something to do with the valve train.

Either jake brake or part of the variable valve timing.

Other poster is right, either something came loose, or was never torqued from the factory correctly. Make sure on re-install it is torqued correctly and loc-tite is used properly(may or may not supposed to be used).

In the future, when you do valve sets, get them to check these items for proper torque. Even just the engine twisting from torque can loosen things up.

[wildkat]

OK something to do with the valve train.

Either jake brake or part of the variable valve timing.

Other poster is right, either something came loose, or was never torqued from the factory correctly. Make sure on re-install it is torqued correctly and loc-tite is used properly(may or may not supposed to be used).

In the future, when you do valve sets, get them to check these items for proper torque. Even just the engine twisting from torque can loosen things up.

Well that's how I KNEW something was definitely NOT right! My jake brake wasn't working properly...can you imagine coming down the Roger's Pass or the backside of the Coq & not having your jake up to snuff? That's what I was doing... & the power loss...I mean I can pass 5 axles climbing mountains with a Rocky...crap I thought I was back to the old days with a 300hp engine!

Makes sense that they're all tied together!

Thanks allan I will remember to have those things checked...my main mechanic (darling husband) already knows to put the torque wrench on the turbo bolts, so I will be sure to add those to my list too!

[allan5oh]

sounds good to me, just make sure to use the correct torque sequence and amount of torque.

[wildkat]

Absolutely...nice thing about having TWO licensed heavy duty mechanics (his brother & mine) in the family, they've got ALL the proper specs for damned near EVERYTHING!

[Maniac]

What did they do? Buy a shipment of defective bolts for crissake?

I don't think the bolts are defective, just not strong enough.

They are hardened studs and nuts, best and strongest you can use, apparently they are just not strong enough, just like the exhaust manifold studs, strongest you can get in that size, but they break anyway.

Exhaust studs won't cause anything to happen except a blown exhaust gasket, and they always break one at a time, there are 12, I usually wait till at least 4 maybe 5 break, then change them all, if you've never broke any its not IF they will break, just WHEN.

Keep your eye on the exhaust manifold studs,although you WILL hear the leak.

[allan5oh]

Breakage of studs is usually from excess movement, which is usually from looseness. Although those c15's have so much torque they might be flexing the block slightly. I know you can break brackets that way on some engines.

Studs will slowly stretch from heat cycles, creating looseness. Of course it might be impossible to tighten them after a while.

[wildkat]

I don't think the bolts are defective, just not strong enough.

They are hardened studs and nuts, best and strongest you can use, apparently they are just not strong enough, just like the exhaust manifold studs, strongest you can get in that size, but they break anyway.

Exhaust studs won't cause anything to happen except a blown exhaust gasket, and they always break one at a time, there are 12, I usually wait till at least 4 maybe 5 break, then change them all, if you've never broke any its not IF they will break, just WHEN.

Keep your eye on the exhaust manifold studs,although you WILL hear the leak.

LOL now that's funny...ever heard a C15 with no muffler? I was leaving the city late one night...I think I'd had my truck maybe a week...the exhaust clamp that comes right off the manifold..is that the right term with a diesel?... anyway it blew off...I have one of those fancy retro exhausts that looks like I'm running straight pipes, but I actually have one HUGE muffler mounted between the frame rails..damned near the size of a 45 gallon drum! MAN...the guys at Peterbilt said they could here me coming from 6 blocks away!

But I have had ALL of my exhust bolts changed, a couple broke around the time I took my truck in for the last factory warranty check up...I took it in for a total go over...just before the factory warranty came off...cause it's bumper to bumper. LOL they fixed ALOT of stuff! All minor, but broken bolts, that sort of thing.

[wildkat]

Breakage of studs is usually from excess movement, which is usually from looseness. Although those c15's have so much torque they might be flexing the block slightly. I know you can break brackets that way on some engines.

Studs will slowly stretch from heat cycles, creating looseness. Of course it might be impossible to tighten them after a while.

You know I wondered about that too allan, I also wondered about the extreme temperatures I run in way up north, then coming down to warmer...well I guess that's relative...but when you go from -60 to -20 that IS quite a difference, & I often wonder if that might cause extra stress.

[Maniac]

Breakage of studs is usually from excess movement, which is usually from looseness. Although those c15's have so much torque they might be flexing the block slightly. I know you can break brackets that way on some engines.

Studs will slowly stretch from heat cycles, creating looseness. Of course it might be impossible to tighten them after a while.

Cat solved the block flexing by the steel spacers one under the head and one above the oil pan.

The exhaust studs are definitly temp related, but not outside temp, just the manifold and turbo heat, those twin turbos put out some unreal heat, have you cooked the air cooler boots by the turbo yet?

And yes, the manifold "moves" the studs are too small at 3/8" Cummins use 1/2" on theirs.

The jake studs like you broke are also exposed to high torque from the jake, and are probably too small also.

[allan5oh]

Thing is the manifold needs to move. Not under the studs though.

If the manifold(all I've seen are 3 piece style) seizes together, you're going to have massive broken studs/bolts.

[Maniac]

Thing is the manifold needs to move. Not under the studs though.

If the manifold(all I've seen are 3 piece style) seizes together, you're going to have massive broken studs/bolts.

True, the Cat studs are just too small at 3/8"